I. Field of the Invention
The invention pertains to an antenna arrangement for transmitting and receiving electromagnetic signals as well as to glazings furnished with such antenna arrangements.
II. Description of Related Art
The receiving and transmitting of electromagnetic waves call particularly upon crossed-dipole antennas. Such an antenna is known, for example, from Patent DE 699 05 436 T2. The drawback of this crossed-dipole antenna resides in the fact that it exhibits an excessive height for certain applications.
If a small height is necessary, the antennas used in the art of high frequencies are frequently so-called patch antennas with which the antenna proper is composed of a patch. With such antennas, the patch and the feed cable have to frequently exhibit the same layered structure, which amounts to saying that the material of the substrate and the height of the substrate are identical for the supply cable and the patch. In this case it is difficult to find a good compromise between the requirements imposed on the feed cable, it should neither transmit nor receive, and on the antenna itself, it should transmit or receive as well as possible.
In the technical field of traffic flow, devices which demand wireless communication are being employed more and more often. Communication applications of this type are, for example, centralized traffic guidance or electronic toll collection (ETC). The frequency used for these applications is generally of the order of 5.8 GHz (microwave frequencies). The antennas for these frequencies are also called DSRC antennas (standing for Dedicated Short Range Communication). In the field of ETC, an onboard DSRC unit (OBU On-Board Unit) for motor vehicles is known from U.S. Pat. No. 6,421,017 B1. This OBU comprises an antenna and a control unit for communication with transmitter/receiver devices that are disposed along the path travelled. The innovation according to the above American patent resides in the fact that the OBU is modified in such a way that it can be installed on the dashboard at a given distance from the windscreen. This makes it possible to avoid the characteristics of the antenna being too dispersed on account of the various gaps between the antenna and the glazing following inaccurate mounting. The drawback with this arrangement is that the location of mounting of the OBU is not variable. Another drawback appears when a glazing has to be covered with a layer reflecting electromagnetic waves. In this case, data transmission is possible only if a corresponding communication window is provided in the coating. The manufacture of such a communication window is however frequently tied to increased complexity and increased cost.